Bimetal thermostat



UNITED, STATES PATENT OFFICE.

BIMETAL THERMO STAT Howard Scott, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Application April 23, 1930. Serial No. 446,779

Claims. (01. 297-15) My invention relates to thermally actuable deponents substantially the same, in order that both vices and particularly to bi-metallic thermostats. components may respond in substantially the The main object of my invention is to provide same degree, to the rolling and other fabricating a bi-metallic thermostat which shall have improcesses. It may be necessary to adjust the 5 proved fabricating properties, relatively high deamount of beta constituent in the brass by a con- 60 flection for a' predetermined temperature change trol in regard to the amount of zinc and of aluand which shall retain its inherent strength up minum for a given relation of copper to nickel to to a relatively high temperature. manganese, in order that substantially the same Another object of my invention is to provide a range of hardness changes may be obtained in highly efficient bi-metal thermostat that shall be the high expansion component, during the cold-' 65 adapted for use in the control of relatively low rolling process, as exists in the low-expansion temperature values while maintaining all of the component, desirable characteristics as to strength and de- I have illustrated a bi-metal bar including a flection. h gh-expansion member 11 and a low-expansion In practicing my invention, I provide a highmember 12 suitably united, as by welding, each m expansion component including major and submember being of the composition hereinafter t stantially equal portions of copper, nickel and forth. zinc and with or without admixtures of minor A representative list of percentages of the vaportions of aluminum and manganese. The lowrious metals which I prefer to utilize in my im 0 expansion component of the combination is a ferproved high-expansion component is given below: to

rous alloy containing a major portion of iron, a minor portion of nickel and relatively small quan- H19, 1 expansion component tities of cobalt and manganese and a still smaller quantity of carbon. %Zn %A1 76MB The single figure of the drawing is a sectional 9@ view of a bi-metal bar embodying my invention. 5 g 9 8 0 When brass is used as the high-expansion coma 5010 23: 4 2010 0 8 ponent of a bi-metal thermostat, the temperag 0 ture range over which a combination including a 0 3510 32I0 3010 3 3 high-expansion component of brass may be used @5 is relatively limited. The fabricating characteristics of a bi-metal element of the kind having a A table of preferred compositions of the 1owcopper base component leave much to be desired. expansion component of my improved bimetal The high-expansion component in this case, is thermostat is given below.

35 the softer, and it is highly desirable that its hardgg ness characteristic be increased and, in the case Low expansion component of copper-base alloys, this requires the introduction of constituent or metal which will not mate- N0. %Ni %0 Remainder rially decrease the solid solubility of zinc. I have 40 found that nickel accomplishes this function very 1 35-39 20 0. 2-0.5 0-0.3 Fe impug, as

effectively and, at the same time, materially ing $318 0 8 i 1: ii :1 creases the high-temperature strength of the 4 28.7 1.3 '0.7' 0.1 component over that of the basic copper-zinc al- 5 loys. Aluminum 'and manganese may also be added with substantial benefits to the strength I have found that bi-meta'l thermostats, in N8 of the component at high temperatures. Alumiwhich the cooperating component include one or num may be considered as a substitute for zinc, another CO b n Of a oys ve above in the and manganese may be considered as a substitute two tables have improved fabricating characterfor copper lstics, particularly as to their having substantial- When a brass-base alloy is combined with a ly the same degrees of hardness. I have found ferrous alloy to constitute a bi-metallic thermoalso that bi-metal thermostats made of alloy stat, the problem of similar hardness values of of this kind will have a highe temperature range the two components may have to be considered. in the low-temperature field without loss of sensi- It is, of course, obvious that it is highly desirable tivity or deflection than the bi-metallic thermoto have the hardness of the two bi-metal com- Stats which have been in use heretofore and ills which utilized, as their high-expansion component a plain brass, or pure copper-zinc alloy.

Various modifications may be made in the device embodying my invention and I desire, therefore, that only such limitations shall be placed thereon as are set forth in the appended claims.

I claim as my invention:

l. A thermostatic element comprising a pair of cooperating metallic members having difierent temperature coeflicients of expansion, the member having the higher temperature coemcient of expansion being an alloy including from 20% to 40% nickel, 60% to 25% copper and 20% to 35% zinc and the member having the lower temperature coemcient of expansion being an iron alloy including from 30% to 39% nickel, from 2% to 10% cobalt and traces of manganese and carbon.

2. A thermostatic element comprising a pair of cooperating metallic members having different temperature coemcients of expansion, the highexpansion member including substantially thirty to thirty three and one third per cent each of copper, nickel and zinc and the low-expansion member consisting of substantially thirty three per cent nickel, between two and ten per cent cobalt, traces of carbon and manganese, the remainder being iron.

3. A thermostatic element comprising a pair of metallic members having different temperature coei'ficients of expansion, the member having the higher temperature coefiicient of expansion being per cent and ten the remainderbeing an alloy including substantially thirty to thirtythree and one-third per cent each of nickel, copper and zinc, and the member having the lower temperature coeiiicient of expansion being an alloy including between twenty-seven per cent and thirty-two per cent of nickel, between two per cent of cobalt, between two tenths and eight tenths per cent of manganese, between one tenth and three tenths per cent of carbon, the remainder being iron.

i. A thermostatic element comprising a pair of cooperating metallic members having different temperature coefiicients of expansion, the highexpansion member consisting of substantially thirty-three per cent each of copper and of nickel, slightly less than thirty-three per cent of zinc, the remainder being aluminum, the low-expansion member including slightly less than thirtythree per cent of nickel, two per cent to ten per cent of cobalt, traces of each of manganese and carbon, the remainder being iron.

5. A thermostatic element comprising a pair of cooperating metallic members having different temperature coefiicients of expansion, the highexpansion member consisting of substantially thirty per cent each of copper, nickel and zinc, the remainder being manganese, the low-expansion member consisting of substantially thirtythree per cent nickel, from two to ten per cent cobalt, between two tenths and eight tenths of Lie one per cent of manganese and a trace of carbon,

iron.

HOWARD SCOTT. 

